The present invention relates to a fuel tank having a venting system for reduced fuel permeation.
Blow-molded fuel tanks are known and have been widely used in industries such as the automotive industry. Vapor valving is a common way of venting a gaseous fluid at a particular pressure from a blow-molded fuel tank containing liquid and gaseous contents. In many venting systems of blow-molded fuel tanks, a gaseous fluid is vented through a typical venting valve which is disposed within a surface or tank shell of the tank of a vehicle. The gaseous fluid flows through a connection port of the valve, wherein the port is located outside the tank during operation of the valve. The connection port is in fluid communication with a permeation barrier hose through which the gaseous fluid flows to be received in a separate vapor canister within the vehicle for further processing.
The above-mentioned system is adequate but can be improved. For instance, the venting valve, which typically is made of a different material than the tank shell, is welded to attach to the tank shell with a permeation barrier material, e.g., nylon. This creates a weld having two different coefficients of thermal expansion, wherein surface contact is typically continuously maintained. In many situations, this often results in delamination of the materials from each other.
Moreover, current fuel tank configurations may be prone to fuel permeation during use. That is, when the tank contains hydrocarbons therein, hydrocarbon absorption occurs within layers of the shell, creating hydrocarbon “swelling” of the tank. As a result, the aperture through which the venting valve is disposed expands due to the absorption of hydrocarbons and the hydrocarbon swelling of the tank. In many situations, the swelling opens a path of hydrocarbon permeation through the tank to the atmosphere. However relatively small, this too is undesirable.
In addition, the cost of such venting system is relatively high, since materials required to manufacture or purchase the permeation barrier hose is relatively expensive. Such permeation barrier hose may comprise a significant portion relative to the entire cost of manufacturing the venting system.